D/A Resolution Impact on a Poly-phase Multipath Transmitter

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    In recent publications the Poly-phase multipath technique has been shown to produce a clean output spectrum for a power upconverter (PU) architecture. The technique utilizes frequency independent phase shifts before and after a nonlinear element to cancel out the harmonics and sidebands due to the nonlinearity. A major advantage of this technique is that it circumvents the need to use dedicated RF filters which makes it a potential candidate for cognitive radio transmitters. This paper addresses the requirements on the digital and mixed signal part of such a transmitter. An architecture is proposed based on complex multiplication which can be used to generate the digital multiphase signals required by the multipath technique. Due to equal phase difference of all the paths the same digital hardware could be utilized for carrying out all the phase shifts. When the digital signals pass through a D/A converter which doesn’t have a reconstruction filter, the output in this case would be amplitude discrete like that of a zero order hold. The spectrum of this amplitude discrete signal would have distortion components in it. This can be termed as quantization distortion but now in the context of limited D/A resolution. The multipath technique’s effect on harmonic cancellation, in the presence of such a quantization distortion is explored in this paper. It is shown through simulation that when using ideal phase shifts the multipath technique is able to cancel most of the harmonics produced by an amplitude discrete representation of pure sinusoids. When (upconversion) mixers are used for the second set of phase shifts then with multipath the highest quantization spurs go down with roughly 8db/bit for a single tone and around 10db/bit for two tone inputs.
    Original languageUndefined
    Title of host publicationProceedings of the 19th Annual Workshop on Circuits
    Place of Publicationveldhoven
    Number of pages7
    ISBN (Print)978-90-73461-56-7
    Publication statusPublished - 27 Nov 2008
    Event19th Annual Workshop on Circuits, Systems and Signal Processing, ProRISC 2008 - Veldhoven, Netherlands
    Duration: 27 Nov 200828 Nov 2008
    Conference number: 19

    Publication series

    PublisherTechnology Foundation STW


    Conference19th Annual Workshop on Circuits, Systems and Signal Processing, ProRISC 2008


    • EWI-14971
    • METIS-255460
    • IR-65347

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